From d6cb986d722bf65035763df8b7cf10ddb7285d30 Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Sat, 20 Mar 2021 02:29:29 -0400
Subject: [PATCH] [pixel] multiplex sprixel_cell_wipe()

---
 src/demo/yield.c   | 4 ++++
 src/lib/internal.h | 7 +++++++
 src/lib/render.c   | 9 +++++++++
 src/lib/terminfo.c | 2 ++
 4 files changed, 22 insertions(+)

diff --git a/src/demo/yield.c b/src/demo/yield.c
index cea7693b2..03b598730 100644
--- a/src/demo/yield.c
+++ b/src/demo/yield.c
@@ -6,6 +6,10 @@ int yield_demo(struct notcurses* nc){
   }
   int dimy, dimx;
   struct ncplane* std = notcurses_stddim_yx(nc, &dimy, &dimx);
+  // in sixel-based implementation, if we redraw each cycle, the underlying
+  // material will be redrawn, taking time. erasing won't eliminate the
+  // flicker, but it does minimize it.
+  ncplane_erase(std);
   char* pic = find_data("worldmap.png");
   struct ncvisual* wmv = ncvisual_from_file(pic);
   free(pic);
diff --git a/src/lib/internal.h b/src/lib/internal.h
index 2f146710a..2987578fc 100644
--- a/src/lib/internal.h
+++ b/src/lib/internal.h
@@ -315,6 +315,10 @@ typedef struct tinfo {
   bool sixel_supported;  // do we support sixel (post pixel_query_done)?
   int sprixelnonce;      // next sprixel id
   int (*pixel_destroy)(struct notcurses* nc, const struct ncpile* p, FILE* out, sprixel* s);
+  // wipe out a cell's worth of pixels from within a sprixel. for sixel, this
+  // means leaving out the pixels (and likely resizes the string). for kitty,
+  // this means dialing down their alpha to 0 (in equivalent space).
+  int (*pixel_cell_wipe)(sprixel* s, int y, int x);
   bool pixel_query_done; // have we yet performed pixel query?
   bool sextants;  // do we have (good, vetted) Unicode 13 sextant support?
   bool braille;   // do we have Braille support? (linux console does not)
@@ -1257,6 +1261,9 @@ ncdirect_bg_default_p(const struct ncdirect* nc){
   return channels_bg_default_p(ncdirect_channels(nc));
 }
 
+int sprite_sixel_cell_wipe(sprixel* s, int y, int x);
+int sprite_kitty_cell_wipe(sprixel* s, int y, int x);
+
 int sixel_blit(ncplane* nc, int linesize, const void* data, int begy, int begx,
                int leny, int lenx, const blitterargs* bargs);
 
diff --git a/src/lib/render.c b/src/lib/render.c
index ffbd4fa9f..9694d7556 100644
--- a/src/lib/render.c
+++ b/src/lib/render.c
@@ -922,6 +922,11 @@ emit_bg_palindex(notcurses* nc, FILE* out, const nccell* srccell){
   return 0;
 }
 
+int sprite_kitty_cell_wipe(sprixel* s, int y, int x){
+  // FIXME
+  return 0;
+}
+
 int sprite_kitty_annihilate(notcurses* nc, const ncpile* p, FILE* out, sprixel* s){
   (void)p;
   (void)nc;
@@ -931,6 +936,10 @@ int sprite_kitty_annihilate(notcurses* nc, const ncpile* p, FILE* out, sprixel*
   return 0;
 }
 
+int sprite_sixel_cell_wipe(sprixel* s, int y, int x){
+  return 0; // FIXME
+}
+
 int sprite_sixel_annihilate(notcurses* nc, const ncpile* p, FILE* out, sprixel* s){
   (void)out;
   struct crender* rvec = p->crender;
diff --git a/src/lib/terminfo.c b/src/lib/terminfo.c
index 73ffb5ec2..391984561 100644
--- a/src/lib/terminfo.c
+++ b/src/lib/terminfo.c
@@ -60,6 +60,7 @@ apply_term_heuristics(tinfo* ti, const char* termname){
     ti->sextants = true; // work since bugfix in 0.19.3
     ti->pixel_query_done = true;
     ti->sixel_supported = true;
+    ti->pixel_cell_wipe = sprite_kitty_cell_wipe;
     ti->pixel_destroy = sprite_kitty_annihilate;
     set_pixel_blitter(kitty_blit);
   /*}else if(strstr(termname, "alacritty")){
@@ -346,6 +347,7 @@ query_sixel(tinfo* ti, int fd){
             ti->sixel_supported = true;
             ti->color_registers = 256;  // assumed default [shrug]
             ti->pixel_destroy = sprite_sixel_annihilate;
+            ti->pixel_cell_wipe = sprite_sixel_cell_wipe;
             ti->sixel_maxx = ti->sixel_maxy = 0;
           }
         }